Aircraft commonly use a stack of alternatingly interleaved brake discs for braking the aircraft. As the brake disc stack is used, the discs wear and the aggregate of that wear reduces the thickness of the stack. As a result, the thermal capacity and structural integrity of the brake disc stack changes.
When the stack reaches a predetermined threshold, there is a need to service the stack by replacing the rotors and stators thereby returning the stack to its original thickness. Various approaches have been employed in the past for monitoring when this refurbishing must take place. The most basic type of monitoring includes periodic visual inspection of the brake disc stack itself. Other techniques have relied upon the observation of a wear pin, which is in operative communication with the stack itself. Other techniques have employed a proximity detector or a linear variable differential transformer or the like providing an output signal corresponding to the remaining thickness of the stack.
In the past, the techniques used for monitoring brake wear in aircraft brake disc stacks have been time consuming, somewhat inaccurate, given to problems with the environment and ambient conditions within which they operate, and intrusive into the brake assembly system itself.